The present invention relates to dispensing cartridges for flowable substances.
Dispensing cartridges, in particular for two or more components, are increasingly used in areas where only small quantities are required or in conditions of very limited space. As examples, dispensing cartridges may be used in the repair of electric or electronic apparatus and do-it-yourself applications. The cartridges are typically made of synthetic materials and are preferably manufactured by injection-molding.
One type of known dispensing appliance is characterized in that the cartridges are not seized by their collar, i.e. not near the dispensing nozzle. When maintained by the collar, the pressure applied by the dispensing piston is directly taken up by the retainer of the dispensing appliance. Instead, the dispensing appliance retains the cartridges by a flange at the bottom, i.e. at the end opposite the dispensing opening of the cartridge. This is advantageous in that only the cartridge itself enters into the area of application. It is thus possible to dispense a flowable substance even to hardly accessible locations.
As the cartridge of these dispensing appliances is only retained at the bottom, and since the pressure applied to the cartridge body by the dispensing piston must consequently be transmitted from the tip to the holding flange and from there to the dispensing appliance, the cartridge itself, and particularly its holding flange, must be correspondingly sturdy. In the case of multiple component substances which are only mixed in an attached mixing tube at the time of dispensing, or with high-viscosity substances, considerable forces are generated even in relatively small cartridges having capacities in the milliliter range. These problems are additionally aggravated by the fact that also for reasons of environmental protection, smaller cartridges with a minimal mixing volume, and thus, with a smaller overall residual volume are desired. However, such cartridges require greater pressures for dispensing due to the smaller cross-section of the attached mixing tube. The cartridge bodies can be adapted to these increased requirements by a reinforcement of the walls. The retaining flange, in contrast, tends to bend, to break loose or to slip out from the adapter of the retaining device.
Hitherto it has been common practice to ensure transmission of forces from the dispensing appliance to the cartridges by as complete a retention of the retaining flange as possible on all sides, and more particularly, close to the cylindrical cartridge bodies. However, these dispensing appliances are expensive and only applicable in a limited range of cartridge sizes. One of the characteristics of simpler and lower-priced dispensing appliances, as e.g. described in EP-B-0,291,753 to the applicant, is that the retaining flange at the bottom of the cartridge is not held completely, resulting in locally increased stresses of the latter. On the other hand, reinforcement of the retaining flange is limited by the preferred manufacturing technique of injection-molding, and its strengthening by this method would also lead to inacceptable costs as compared to the obtainable results.
Analogous problems appear with respect to dispensing appliances retaining the cartridge by the collar. In this case as well, the cartridges often require a reinforcement of the dispensing opening. Especially in the case of multiple component cartridges with mixing ratios greatly differing from 1:1, one of the cartridge bodies is very lean, and a strong collar in the form of a disk near the dispensing opening must be provided in order to create a good support for the adapter of the dispensing appliance. Here also, an incomplete retention by the dispensing appliance, in particular, may lead to deformations as described above, and thus to an unprecise dispensing and mixing process.